<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title>DbStream::read()</title>
    <link rel="stylesheet" href="apiReference.css" type="text/css" />
    <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
    <link rel="start" href="index.html" title="Berkeley DB C++ API Reference" />
    <link rel="up" href="blob.html" title="Chapter 14.  External Files" />
    <link rel="prev" href="dbstream_close.html" title="DbStream::close()" />
    <link rel="next" href="dbstream_size.html" title="DbStream::size()" />
  </head>
  <body>
    <div xmlns="" class="navheader">
      <div class="libver">
        <p>Library Version 12.1.6.2</p>
      </div>
      <table width="100%" summary="Navigation header">
        <tr>
          <th colspan="3" align="center">DbStream::read()</th>
        </tr>
        <tr>
          <td width="20%" align="left"><a accesskey="p" href="dbstream_close.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 14. 
                External Files
        </th>
          <td width="20%" align="right"> <a accesskey="n" href="dbstream_size.html">Next</a></td>
        </tr>
      </table>
      <hr />
    </div>
    <div class="sect1" lang="en" xml:lang="en">
      <div class="titlepage">
        <div>
          <div>
            <h2 class="title" style="clear: both"><a id="dbstream_read"></a>DbStream::read()</h2>
          </div>
        </div>
      </div>
      <pre class="programlisting">#include &lt;db_cxx.h&gt;
 
int
DbStream::read(Dbt *data, db_off_t offset, u_int32_t size, 
               u_int32_t flags); </pre>
      <p>
        The <code class="methodname">DbStream::read()</code> method reads
        <span class="bold"><strong>size</strong></span> bytes from the external file,
	starting at <span class="bold"><strong>offset</strong></span>, into the
        DBT <span class="bold"><strong>data</strong></span>.
     </p>
      <p>
         The stream is created using <a class="xref" href="dbstream.html" title="Dbc::db_stream()">Dbc::db_stream()</a>.
     </p>
      <p>
         Unless otherwise specified, the
         <code class="methodname">DbStream::read()</code> <span>
            
            <span>
                method either returns a non-zero error value or throws an
                exception that encapsulates a non-zero error value on
                failure, and returns 0 on success.
            </span>
        </span>
    </p>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm139670054425280"></a>Parameters</h3>
            </div>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idm139670054426528"></a>data</h4>
              </div>
            </div>
          </div>
          <p>
                  The <span class="bold"><strong>data</strong></span> parameter is
                  the <a class="link" href="dbt.html" title="Chapter 4.  The Dbt Handle">Dbt</a> into which you
                  want to place the data read using this method.
             </p>
          <p>
                 Note that the data DBT must be set with one of the
                 following flags, or this method will return an error:
                 <a class="link" href="dbt.html#dbt_DB_DBT_MALLOC">DB_DBT_MALLOC</a>, 
                 <a class="link" href="dbt.html#dbt_DB_DBT_REALLOC">DB_DBT_REALLOC</a>, 
                 <a class="link" href="dbt.html#dbt_DB_DBT_USERMEM">DB_DBT_USERMEM</a>, or
                 <a class="link" href="dbt.html#dbt_DB_DBT_APPMALLOC">DB_DBT_APPMALLOC</a>.
             </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idm139670054452096"></a>offset</h4>
              </div>
            </div>
          </div>
          <p>
                  The <span class="bold"><strong>offset</strong></span> parameter
                  indicates the starting position, in bytes, from the
                  beginning of the external file where you want the read to
                  begin.
             </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idm139670054466544"></a>size</h4>
              </div>
            </div>
          </div>
          <p>
                  The <span class="bold"><strong>size</strong></span> parameter
                  indicates the number of bytes to read.
             </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idm139670054452512"></a>flags</h4>
              </div>
            </div>
          </div>
          <p>
                  The <span class="bold"><strong>flags</strong></span> parameter must be set to 0.
             </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm139670054432528"></a>Errors</h3>
            </div>
          </div>
        </div>
        <p>
             The <code class="methodname">DbStream::read()</code> <span>
            
            <span>
                method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> 
                exception, encapsulating one of the following non-zero errors, or return one
                of the following non-zero errors:
            </span>
        </span>
        </p>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idm139670054406160"></a>DB_BUFFER_SMALL</h4>
              </div>
            </div>
          </div>
          <p>
                The Dbt provided to this method was not configured
                appropriately, and so there is not enough space allocated
                for the bytes you are trying to read.
            </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idm139670054419888"></a>EINVAL</h4>
              </div>
            </div>
          </div>
          <p>
                An invalid flag value or parameter was specified; or if the 
                Dbt was configured with 
                <a class="link" href="dbt.html#dbt_DB_DBT_PARTIAL">DB_DBT_PARTIAL</a>.
            </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm139670054416832"></a>Class</h3>
            </div>
          </div>
        </div>
        <p>
            <a class="link" href="blob.html" title="Chapter 14.  External Files">DbStream</a>  
        </p>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm139670054421952"></a>See Also</h3>
            </div>
          </div>
        </div>
        <p>
             <a class="xref" href="blob.html#bloblist" title="External Files and Related Methods">External Files and Related Methods</a> 
        </p>
      </div>
    </div>
    <div class="navfooter">
      <hr />
      <table width="100%" summary="Navigation footer">
        <tr>
          <td width="40%" align="left"><a accesskey="p" href="dbstream_close.html">Prev</a> </td>
          <td width="20%" align="center">
            <a accesskey="u" href="blob.html">Up</a>
          </td>
          <td width="40%" align="right"> <a accesskey="n" href="dbstream_size.html">Next</a></td>
        </tr>
        <tr>
          <td width="40%" align="left" valign="top">DbStream::close() </td>
          <td width="20%" align="center">
            <a accesskey="h" href="index.html">Home</a>
          </td>
          <td width="40%" align="right" valign="top"> DbStream::size()</td>
        </tr>
      </table>
    </div>
  </body>
</html>
